1. Field of the Invention
Numerous plasmid elements have been developed as cloning vehicles in Escherichia coli. While there have been numerous developments with E. coli, and numerous opportunities still remain, there will be many situations where other microorganisms will be of interest or be required for a particular purpose. In addition, the ability to transform other microorganisms will be a powerful tool in the genetic analysis of species, particularly where other genetic systems are unavailable. Furthermore, vectors could be used to augment or modify desirable characteristics of the host bacterium, such as nitrogen fixation by Rhizobium species or hydrocarbon degradation by Pseudomonas species.
A suitable vector should have a wide range of desirable properties. These properties should provide for efficient introduction of exogenous DNA, allow for high efficiency of introduction of the plasmid into the host bacteria, provide stable maintenance in exconjugants and not confer hazardous properties to the host. In addition, the plasmid should not be readily transmissible.
2. Description of the Prior Art
Meyer et al., DNA Insertion Elements, Plasmids, and Episomes, 1977, Cold Spring Harbor Laboratory, pp. 599-566, describes the properties of the plasmid RK2 as a cloning vehicle. The regions necessary for DNA replication of RK2 are described by Meyer and Helinski (1977), Biochim. Biophys. Acta. 478, 109-113, and Thomas and Helinski (1979), J. Bacteriol. 141, 213. The site for conjugal mobilizability in RK2 is described by Guiney and Helinski (1979), Mol. Gen. Genet. 176, 183-189.